Summitt Syndrome

Topic Contents

Summitt Syndrome

National Organization for Rare Disorders, Inc.

Important It is possible that the main title of the report Summitt Syndrome is not the name you expected. Please check the
synonyms listing to find the alternate name(s) and
disorder subdivision(s) covered by this report.

Synonyms

Summitt's Acrocephalosyndactyly

Disorder Subdivisions

None

Related Disorders List

Information on the following diseases can be found in the
Related Disorders section of this report:

Apert Syndrome (Acrocephalopolysyndactyly Type I)

Carpenter Syndrome (Acrocephalopolysyndactyly Type II)

Sakati-Nyhan Syndrome (Acrocephalopolysyndactyly Type III)

Goodman Syndrome (Acrocephalopolysyndactyly Type IV)

Pfeiffer Syndrome (Acrocephalopolysyndactyly Type V)

Acrocephalopolysyndactyly, Robinow-Sorauf Type

General Discussion

Summitt syndrome is an extremely rare genetic disorder characterized by malformations of the head, abnormalities of the hands and/or feet, and obesity. The syndrome is inherited as an autosomal recessive genetic trait. Some researchers believe that Summitt syndrome is one of seven closely related forms of a disorder characterized by characteristic malformations of the head and webbing between several toes and/or fingers (acrocephalopolysyndactyly). The malformations of the head are the result of the premature closings of the seams (cranial sutures) between the bony plates that make up the skull. Of the various forms of this disorder, many geneticists believe that Summitt syndrome is closely related to Carpenter syndrome (acrocephalopolysyndactyly type II).

Symptoms

In Summitt syndrome, the fibrous joints between the bones in the skull (cranial sutures) close prematurely (craniosynostosis), causing the head to grow upward at an accelerated rate. As a result, the head appears long, narrow, and pointed at the top (tower skull). Affected individuals also have webbed or fused fingers and/or toes (syndactyly) and are usually extremely overweight (obese). Other features may include vertical folds of skin over the eyes' inner corners (epicanthal folds), delayed tooth eruption, an abnormally narrow roof of the mouth (palate), a malformed hip joint (coxa valga), and/or knock knees, that is, knees that are abnormally close together and ankles that are abnormally wide apart (genu valgum). Males with Summitt syndrome may have an abnormal enlargement of one or both breasts (gynecomastia). Intelligence is typically within normal limits.

Causes

Summitt syndrome is inherited as an autosomal recessive trait. The precise location of the changed gene has not yet been determined.

Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome and females have two X chromosomes. Each chromosome has a short arm designated "p" and a long arm designated "q". Chromosomes are further sub-divided into many bands that are numbered. For example, "chromosome 11p13" refers to band 13 on the short arm of chromosome 11. The numbered bands specify the location of the thousands of genes that are present on each chromosome.

Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.

Recessive genetic disorders occur when an individual inherits the same abnormal gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and, therefore, have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%. The risk is the same for males and females.

All individuals carry a few abnormal genes. Parents who are close relatives (consanguineous) have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk to have children with a recessive genetic disorder.

Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary for the appearance of the disease. The abnormal gene can be inherited from either parent, or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy regardless of the sex of the resulting child.

Affected Populations

Summitt syndrome is an extremely rare disorder that is believed to affect males and females in equal numbers. There have been too few cases reported to determine whether the disorder is more prevalent among males or females. The number of affected individuals is thought to number only about 12, of whom at least two were the children of closely related parents.

Related Disorders

Symptoms of the following disorders can be similar to those of Summitt syndrome. Comparisons may be useful for a differential diagnosis:

Acrocephalopolysyndactyly (ACPS) is a group of very rare genetic disorders including Apert syndrome [along with Noack syndrome] (Type I), Carpenter syndrome (Type II), Sakati-Nyhan syndrome (Type III), Goodman syndrome (Type IV) and Pfeiffer syndrome Type V). All of these types of ACPS are characterized by a long, narrow head that appears pointed at the top (acrocephaly), more than the usual number of fingers and/or toes (polydactyly), and webbing of fingers and/or toes (syndactyly).

Apert syndrome (including Noack syndrome) is a genetic defect and falls under the broad classification of acrocephalopolysyndactyly anomalies. It can be inherited from a parent who has the disorder, or may be a new mutation. It occurs in approximately 1 per 160,000 to 200,000 live births. Apert syndrome is primarily characterized by specific malformations of the skull, midface, hands, and feet. The skull is prematurely fused and unable to grow normally; the midface (the area of the face from the middle of the eye socket to the upper jaw) appears sunken, and the fingers and toes are fused together in varying degrees.

Ordinarily, a child's skull is made up of several plates that remain loosely connected to one another, gradually growing together to form the adult skull. The Apert child's skull, by contrast, has a premature fusion of these plates, restricting brain growth, and causing increased pressure in the brain as it grows. This is known as craniosynostosis or acrocephalopolysyndactyly.

Carpenter syndrome (acrocephalopolysyndactyly type II) is a very rare inherited disorder characterized by a long, narrow head (acrocephaly), abnormally short, webbed fingers (brachysyndactyly), and feet with more than five toes that may also be webbed (polysyndactyly). Affected individuals have characteristic down-slanted eyes, a flattened nasal bridge, broad cheeks, low-set ears, and underdeveloped jaw bones (hypoplastic mandible). Other features may include mild obesity, mental retardation, protrusion of portions of the intestines through the abdominal wall (abdominal hernias), underdeveloped sex organs (hypogenitalism), and congenital heart disease. Carpenter syndrome is inherited as an autosomal recessive genetic trait. Some researchers believe that Summitt syndrome may be a variant of Carpenter syndrome. (For more information on this disorder, choose "Carpenter" as your search term in the Rare Disease Database.)

Sakati-Nyhan syndrome (acrocephalopolysyndactyly type III) is also known as Sakati syndrome or acrocephalopolysyndactyly with leg hypoplasia. It is an extremely rare inherited disorder characterized by malformation of the head (acrocephaly), feet with more than five toes that may be webbed (polysyndactyly); and hands with extra and abnormally short fingers (brachypolydactyly). Deformities of the legs are also present, which may include bowed thigh bones (femurs), abnormally shaped, displaced calf bones (fibulas), and underdeveloped shin bones (hypoplastic tibias). Facial abnormalities may include protruding eyes; an elongated nose, large, low-set ears, and a prominent forehead. Other conditions associated with Sakati-Nyhan syndrome include dental crowding, an underdeveloped upper jaw bone (maxillary hypoplasia), a short neck with a low hairline, absence of hair (alopecia), and congenital heart disease. Intelligence is usually normal. Sakati-Nyhan syndrome is thought to be caused by a genetic change (mutation) in mature parents that occurs for no apparent reason (sporadic). (For more information on this disorder, choose "Sakati" as your search term in the Rare Disease Database.)

Goodman syndrome (acrocephalopolysyndactyly type IV) is an extremely rare genetic disorder characterized by a long, narrow head (acrocephaly) and several facial abnormalities, including a prominent nose, highly arched eyebrows, and vertical skin folds that may cover the eyes' inner corners (epicanthal folds). Abnormalities of the hands and feet may also be present, including webbed fingers and/or toes (syndactyly); extra fingers (postaxial polydactyly); and fifth fingers that are abnormally bent (clinodactyly) and permanently flexed (camptodactyly). Other features may include a deviation of one of the forearm bones (ulna), knees that are abnormally close together and ankles that are abnormally far apart (genu valgum), and congenital heart disease. Intelligence is typically within normal limits. Some researchers believe that Goodman syndrome may be another variant of Carpenter syndrome (Acrocephalopolysyndactyly Type II). Goodman syndrome is inherited as an autosomal recessive trait. (For more information on this disorder, choose "Goodman" as your search term in the Rare Disease Database.)

Pfeiffer syndrome (acrocephalosyndactyly type V) is generally accepted to be the same condition as Noack syndrome (Acrocephalopolysyndactyly Type I). It is a very rare genetic disorder characterized by a short, pointed, or cone-shaped head (acrobrachycephaly) and abnormalities of the face, jaws, and teeth. Individuals with Pfeiffer syndrome may also have webbed fingers or toes (syndactyly), additional abnormalities of the thumbs and big toes, and a mild hearing loss. Intelligence is usually normal. Pfeiffer syndrome is inherited as an autosomal dominant trait. (For more information on this disorder, choose "Pfeiffer" as your search term in the Rare Disease Database.)

Carpenter Syndrome (Acrocephalopolysyndactyly Type II) is a very rare inherited disorder characterized by a long, narrow head (acrocephaly); abnormally short, webbed fingers (brachysyndactyly); and feet with more than five toes that may also be webbed (polysyndactyly). Affected individuals have characteristic downslanted eyes, a flattened nasal bridge, broad cheeks, low-set ears, and underdeveloped jaw bones (hypoplastic mandible). Other features may include mild obesity, mental retardation, protrusion of portions of the intestines through the abdominal wall (abdominal hernias), underdeveloped sex organs (hypogenitalism), and congenital heart disease. Carpenter Syndrome is inherited as an autosomal recessive genetic trait. Some researchers believe that Summitt Syndrome may be a variant of Carpenter Syndrome. (For more information on this disorder, choose "Carpenter" as your search term in the Rare Disease Database.)

Sakati Syndrome (Acrocephalopolysyndactyly Type III) is also known as Sakati-Nyhan Syndrome or Acrocephalopolysyndactyly with leg hypoplasia. It is an extremely rare inherited disorder characterized by malformation of the head (acrocephaly), feet with more than five toes that may be webbed (polysyndactyly), and hands with extra and abnormally short fingers (brachypolydactyly). Deformities of the legs are also present, which may include bowed thigh bones (femurs), abnormally shaped, displaced calf bones (fibulas), and underdeveloped shin bones (hypoplastic tibias). Facial abnormalities may include protruding eyes; an elongated nose, large, low-set ears; and a prominent forehead. Other conditions associated with Sakati Syndrome include dental crowding, an underdeveloped upper jaw bone (maxillary hypoplasia), a short neck with a low hairline, absence of hair (alopecia), and congenital heart disease. Intelligence is usually normal. Sakati Syndrome is thought to be caused by a genetic change (mutation) in mature parents that occurs for no apparent reason (sporadic). (For more information on this disorder, choose "Sakati" as your search term in the Rare Disease Database.)

Goodman Syndrome (Acrocephalopolysyndactyly Type IV) is an extremely rare genetic disorder characterized by a long, narrow head (acrocephaly) and several facial abnormalities, including a prominent nose, highly arched eyebrows, and vertical skin folds that may cover the eyes' inner corners (epicanthal folds). Abnormalities of the hands and feet may also be present, including webbed fingers and/or toes (syndactyly), extra fingers (postaxial polydactyly), and fifth fingers that are abnormally bent (clinodactyly) and permanently flexed (camptodactyly). Other features may include a deviation of one of the forearm bones (ulna), knees that are abnormally close together and ankles that are abnormally far apart (genu valgum), and congenital heart disease. Intelligence is typically within normal limits. Some researchers believe that Goodman Syndrome may be another variant of Carpenter Syndrome (Acrocephalopolysyndactyly Type II). Goodman Syndrome is inherited as an autosomal recessive trait. (For more information on this disorder, choose "Goodman" as your search term in the Rare Disease Database.)

Pfeiffer Syndrome (Acrocephalosyndactyly Type V) is generally accepted to be the same condition as Noack Syndrome (Acrocephalopolysyndactyly Type I). It is a very rare genetic disorder characterized by a short, pointed, or cone-shaped head (acrobrachycephaly) and abnormalities of the face, jaws, and teeth. Individuals with Pfeiffer Syndrome may also have webbed fingers or toes (syndactyly), additional abnormalities of the thumbs and big toes, and a mild hearing loss. Intelligence is usually normal. Pfeiffer Syndrome is inherited as an autosomal dominant trait. (For more information on this disorder, choose "Pfeiffer" as your search term in the Rare Disease Database.)

Antley-Bixler Syndrome is a very rare disorder that is characterized by the abnormal union of adjacent bones (skeletal fusions) in several areas of the body. Individuals with this syndrome exhibit a premature closing of the bones of the skull (craniosynostosis), an incompletely developed midface (hypoplasia), a union between the adjacent bones of the upper and lower arm (radiohumeral synostosis), and fingers that are permanently flexed (camptodactyly). Bowing of the thigh bones (femurs) and fractures of the hip bones are usually present in newborns with this disorder. Affected individuals also exhibit a characteristic facial appearance and ear shape. Although the exact cause of Antley-Bixler Syndrome is not known, it is believed to be inherited as an autosomal recessive genetic trait. (For more information on this disorder, choose "Antley-Bixler" as your search term in the Rare Disease Database.)

Standard Therapies

Summitt syndrome can be detected at birth, based upon a clinical evaluation and characteristic physical findings. Surgical correction of malformations is the primary treatment. Early craniofacial surgery may be performed to correct the premature closure of the bones in the skull (craniosyn-ostosis). Additional craniofacial surgery may be done later in life as well as surgery to correct deformities of the hands and/or feet.

Other treatment is symptomatic and supportive. Genetic counseling will be of benefit for people with Summitt syndrome and their families.

Investigational Therapies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc.® (NORD). Cigna members can access the complete report by logging into myCigna.com. For non-Cigna members, a copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see http://www.rarediseases.org/search/rdblist.html.

The information provided in this report is not intended for diagnostic purposes. It is provided for informational purposes only. NORD recommends that affected individuals seek the advice or counsel of their own personal physicians.

It is possible that the title of this topic is not the name you selected. Please check the Synonyms listing to find the alternate name(s) and Disorder Subdivision(s) covered by this report

This disease entry is based upon medical information available through the date at the end of the topic. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder.

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